Electric zinc-distilling furnace and condenser for producing blue powder.



I. THOMSON.

ELECTRIC ZINC DISTILLING FURNACE AND CONDENSER FOR PRODUCING BLUE POWDER.

APPLICATION FILED JN.28, I9I6.

1,214,842. Patented Feb.6,1917.

4 SHEETS-SHEET I.

I. THOMSON. ELECTRIC ZINC DISTILLING FURNACE AND CONDENSER FOR PRODUCING BLUE POWDER.

APPLICATION FILED .IANI28, |916.

` 1,214,842. Patented Feb. 6, 1917.

4 SHEETS-SHEET 2.

, #Y d. ,sf/ s Arm/MEPs I I. THOMSON.

ELECTRIC ZINC DISTILLING FURNCE AND CONDENSER FOR PRODUCING BLUE POWDER.

APPLICATION FILED 1AN.28, I9I6.

1,214,842. Patented Feb.6,1917,

4 SHEETS-SHEET 3.

5 WWA/55.555: ,ws ATTUR/v s 5. THOMSON.

ELECTRIC ZlNC DISTILLING VFURNCE AND CONDENSER FOR PRODUCING BLUE POWDER.

i APPL-NATION FILED ]AN.28. 1916.

Patented Feb. 6, 1917.

4 SHEETS-SHEET 4.

,OHH....H...........

MTN/55555.

UNITED STATES PATENT OFFICE.

JOHN THOMSON, OF NEW YORK, N. Y., ASSIGNOR TO JOHN THOMSON PRESS COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OE NEW JERSEY.

ELECTRIC ZINC-DISTILLING FURNACE AND CONDENSER FOR PRODUCING BLUE POWDER.

Application filed January 28, 1916.

T all whom t lmay concern.'

Be' 1t known that I, JOHN. THOMSON, a citizen of the United States, and a resident of the borough of Manhattan, city of New York, county and State of New York, have invented certain new and useful Improvements in Electric Zinc-Distilling Furnaces and Condensers for Producing Blue Powder, of which the following is a specification, reference being made to the accompanying drawings, forming a part thereof.

This invention relates to the metallurgy of zinc having particular reference to the purification of impure spelter by distillation in an electric furnace and then condensing, or precipitating, the fume in the forni of blue-powder or dust, and the objects are t0 increase the purity and effectiveness of the said material at a minimum cost of pro* duction.

The accompanying drawings represent a preferred mode of realizing the ends in View, but it will be understood that the invention is not necessarilyy confined to the precise details shown therein. In said drawings,

Figure 1 is a vertical, transverse center section of the furnace and its condenser, of which two are shown in duplicate, as on the line A of Fig. 2.

Fig. 2 is a. half vertical longitudinal center section of the furnace, on its left hand side, as on the line B of Fig. l, while its right hand side is an elevation.

Fig. 3 is a plan View on the plane (l of Fig. 2, kythe forward condenser being shown in horizontal section.

Fig. 4 is a part longitudinal section of the condenser, as on the line D of Fig. 1.

Fig. 5 is an enlarged, detached front elevation of a plate forming a part of the condenser; and s Fig. G is a half end elevation and transverse sectionof said plate.

The heating s ystem of the furnace is comprised in a carbon resistor, E, formed of two slotted plates, 7, 8, producing a zig-zag electric circuit, attached by a connector, 9, to operate in series by electrification from right and left hand terminals, 10, 11.

Beneath the resistor is a shallow trough or open tank, 12, which contains the bath of molten spelter, 13, supplied by a spoilt, 14, located in an end-wall of the furnace.

Specicaton of Letters Patent.

l Patented Feb. 6, 1917.

Serial No. 74,828.

As the rising velocity of the fume from the bath toward the resistor is comparatively slow it becomes more or less super-heated. In order to eliminate some portion of this super-heat and yet to prevent a free upward escape ol'` heat from the resistor itself, an 60 Aoverlying compound septum is provided,

consisting of a lower series of refractory plates` 15, in the ends of which are formed a plurality of ports, 1G, that is two series ot' end ports are disposed along the right and left hand sides of the furnace chamber. Above this lower series of plates is another series, 17, which also have a plurality of ports, 1S; but these are formed in their centers and lie along the longitudinal line B. In this wise there are produced a primary or resistor chamber, H, an intermediary septum chamber, I, and an upper or fume chamber, J. The consequence of this arrangement is that the fume passes 11p-75 through the end ports, 1G, of the lower septum, detlects left and right flowing horizontally across the septum chamber, headon as indicated by arrows a, rises through the center ports, 1S, ot' the upper septum, as 80 indicated by arrows and thence makes a direct impingement against the cover, L, as denoted by arrows, c. The cover consists of several relatively thin refractory tiles or carbon slabs, 19, upon which free bricks, as Q0, may readily be stacked, or removed, to cause a more or less free or a restricted rae diation of heat. The particular objects ot' the, ported septums are to conserve heat in the resistor chamber, ll; to produce a considerable diminution in the temperature of the fume immediately it leaves the upper ports and to thence effect a very perfect volumetric division and a right and left hand deflection thereof, across chamber, J, as indicated by arrows che.

Contrary to the supposition generally entertained by zinc specialists, or expertsf the problem of condensing, or precipitating all, or essentially all, of the fume which cau be evolved in a furnace unit in the form of blue-powder presents many difficulties. The bulk of blue-powder, or zinc-dust, hitherto used in the arts has been a by-product,

a residuum of fume not condensed as fluid metal, which is considerably oxidized (hence the term blue and frequently contains coalesced metal in the form of visible spheres. Excessive oxidization is objectionable as it reduces the purity ot the dust. Excessive oxidization also leads to shotty dust which is objectionable as it` may require screening.

then blue-powder is produced in a high state of perfection, it is in fact a dust ot a ineness of subdivision to which the term impalpable is properlyV applicable; it may assay, in zinc, upward of tlt') pcrcentum and, as to its color, gray would more tittingly apply than blue.

lVhile the foregoing statements, as also others to follow, are more or less academic in character, they are here intrmluced with the, view of possibly making the context clearer. A. given volulne of pure zinc-fun1e. that is fume not associated with vaporized lead, cadmium, mercury, etc., will be precipitated as gray-dust if, lirstly, it does not come in contact with a heated surface whose ten'iperature may range between 4200 and 9230" C.; it', secondly, there is not sutlicient air present to form Zn() and it', thirdly, it is relatively suddenly chilled at temperatures ranging from, say 4000 C. downwardly. Again referring to the drawings, an etlect ot causing a given volume of fume to split. as it were, in the center of the upper chamber and tlow right and lett, according to arrows c is to reduce the lineal velocity ot flow by 5t) percentum as compared to the velocity ot' ilow ot' the same volume when flowing across the chamber in one direction only.

The upper chamberhas no sides, except as relates to a series otl short, narrow pillars 21, Q2, which serve to support thev roofplates; hence, the intervening spaces 23, 2t are virtually extensions ot the chamber and present a low-area effectively equal thereto. The object thereof is to introduce the fume to the condensers, M.' N, at the least possible velocity; in the greatest possible volume and at the utmost uniformity of temperature.

T he condensers extend upwardly from and along the side walls ot the furnace and are preferably constructed from plates of graphitized carbon. Q5, forming relatively narrow but high and long horizontal rectangular chambers, R, S, in tact their lengths are equal to that otl the upper furnace chamber. These plates are excellent conductors of heat and, for some reason not fully known, there appears to be a lesser tendency tor zinc-dust. to adhere thereto than to other available materials. Then, too. graphitized carbon may be readily machined. Each plate is arranged to be water-cooled by means of copper or brass coils, 26, as shown in Figs 1, 5 and 6. this being very eectively accomplished by milling a series, usually touigof parallel lengthwise grooves, 27, in one of the side surfaces. The coil is then laid in the grooves and any free space is tightly packed with a paste chiefly formed of powdered graphite, as 28, Fig. G.

The conswluence is that the entire outer surface of the tubing is brought into intimate physical contact with the plate, where by the transfer otl heat is uniquely elfective. The flow of water through each coil is denoted by arrows t. rlhe cooling water may be caused to circulate through each plate as a distinct unit, or any two or all ot the plates` may be coupled, as indicated in dotted outline, 2t). when the water is caused to circulatej in series. v

lt will now be perceived that immediately the hot fume passes beyond the outer edges ot' the pillars. 21, 22. it is in free space and its tirst impingement, at very low velocity and upon a large surface, viz., upon the vertical surtace olA the lower, outer plates as denoted by arrows .r e, thence reacting and flowing in a natura'l upward direction, as arrows yr more or less tilling, according to the amount ot' prior condensation, the upper reaches olthe condensing chambers. Any h vdrous or other gases may be burned at the vents 30.

The. chilled fume. as a dust, 31, Fig. 1, precipitates and is collected at the bottom upon declined surfaces, 32. 9,3. Between the lower edge ot the lower outer plates and the aforesaid declines are free slit-like spaces 34, 35, normally closed by sharpelged steel plates, acting as valves, 3U, 37, secured against the outer surfaces otl the plates by clips. 3S. 3ft, and having end-handles, as 40, t1. `Whenever a sutlicient quantity of dust will have been collected. a valve is raised and the dust is then free to run out. lVhen the rapidity ot' the l'low of dust indicates that the charge is about exhausted, the valve is practically instantly closed; the flowing stream is shut otl' b v a vertically movable valve and no air can enter thc chamber. 1t l'or any cause the dustv does not run freely, it can readily be released by poking. As the valve isvnot contained within the chambers, it is not liable to become stuck or wedged. or it so a clearance-can readily be etfected. yet in no instance will there be danger ot a back-flow ot air with the consequent possibility ot an explosion.

' Another reason for introducing the fume to the condensers at a loW rate of flow and ,thereafter providing upper chamber spaces ot large volumetric capacity, 1s that the lofthe cloud of fume.

rlhe side and end plates may be. securely bound together by means ot clamps or screws; but the top plates are preferably left free so that, in the event of an explosion, they will blow off. Also, in this wise, either of the condensers can be put out of operation by inserting bricks, or a slab, to stop the flow of fume from the furnace.

The precipitating capacity of a chamber of given volume may be substantially increased by inserting therein a series of spaced plates, 42, conveniently suspended upon a rod 43, as shown at the left hand side of Fig. l and in the detail view, Fig. 4; which serve both to augment the im'pinging surface and the heat conduction.

As previously intimated, thc chilling tempcrature of the interior surfaces of the condensers inust be below the melting point of zinc, or say not higher than about 40()O C. and it may be to any extent lower than that except when hydrous vapor is contained in or with the fume. In such circumstance, the temperature should not be low enough to condense Asuch vapor, or steam, to water which would mix with and produce objectionable cakingof the dust. This condition,

however, is only likely to exist when a furnace is first put into operation and during the drying out interim.,

It is to be observed that the lower surfaces of the spaces containing the supporting pil-l lars are sloped downwardly, and inwardly, as 44, whereby should any fume be condensed thereat to liquid metal it will not run into the condensers, where it would mix with the dust, but back into the furnace and thence through thc septum plates to the trough to be again distilled.

By this system of distilling there is rendered possible the obtaining of a pure Zincsibility of use, as in the manufacture of' anilin dyes. for cyaniding and sherardizmg, not otherwise attainable. Moreover,

under the foregoing conditions, the resistorelement may be run up to higher temperatures than would be permissible in other circumstances, thereby sensibly increasing the thermal efficiency of the furnace.

The vimprovements herein set forth are not limited to the precise construction and arrangement shown and described for they may be embodied in various forms and modifications without departing )from the spirit and scope of the invention.

lVhat I claim is:

l. ln an electric furnace for' distilling fumable metals by means of a radiating resistor suspended above a bath, a compound septum formed of plates suspended above the resistor, the lower series being-provided with a plurality of end ports while the upper series is provided with a plurality of center ports, whereby the fume will first pass upwardly, next in a head-on direction between the two series of septum plates,

thence vertically through the center ports into an overlying chamber and finally in re-, versed right and left hand directions to both sides of an upper chamber.

2. In an electric furnace for distilling spelter having right and left hand condensers, a ported septum throughwhich the hot fume passes into direct Contact with the longitudinal center of the roof, the rate of heat radiation from the roof being controllable, whereby the temperature of the fume ,is reduced prior to entering the condensers.

3. An electric zinc furnace for distilling spelter having an attached condenser, or condensers, adapted to receive zinc-fume from a chamber formed by a ported septum and an overlying roof, the rate of heat-radiation from said root' being controllable, whereby the temperature of the hot fume from the ported septum is reduced, by. contact with the roof, prior to entering the condenser.

rlhis specilication signed and witnessed this 6th day of January, A. l?. 1916.

JOHN THOMSON. Signed in the presence of- J. R. AGNnw, FRED A. KHLER. 

